Schneider - Kreuznach  9519641 Edixa -Xenar 1:2.8/50  is all it has and all that I can tell you, my dad rekons it is a m42 lens mount, and from the checking I have done on internet it appears to be a kodak retina lens but not sure,, want to find out  for sure if I can get an adapter for my nikon D5000   thanks for your interest